I too have experienced problems with the brake light switch. The symptom was
that the switch actually worked fine in isolation: e.g. put an ohm meter
across the leads and press the brake peddle and it worked fine. However,
connect power to the switch and would not carry the current needed to light
the brake lights.
I had this problem on two occasions - with an original switch and with a new
replacement switch.
I do not know how the switch actually works although conceptually it would
seem quite straight forward. Clearly, there is something about the switch
that makes it current sensitive.
I solved the problem by installing a relay. Now the brake switch operates a
relay, which shunts current to the brake lights. The brake switch carries
very little current - only enough to trigger the relay (milliamps). This
solution has worked perfectly. Be advised that I have implemented this
solution on a car using silicon fluid and on a car using standard fluid and
in both cases the solution works fine (for several years now).
As an aside, I used the same set up to operate the horns - again with
perfect results. (Also used this to operate an electric pusher fan on the
Tiger)
The relays I used are can be purchased for a couple of bucks at any auto
parts store. Physically, I mounted the relays in the engine bay on the
passenger side fender flat sheet metal just behind the horn holes.
Wayne
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